Particle Identification in the LHCb Experiment Particle Identification in the LHCb Experiment III...

Particle Identification in the Particle Identification in the

LHCb ExperimentLHCb Experiment

Particle Identification in the Particle Identification in the

LHCb ExperimentLHCb Experiment

III LHC Symposium on Physics and DetectorsIII LHC Symposium on Physics and DetectorsChia, Sardinia, Italy.Chia, Sardinia, Italy.

29 October 2001.29 October 2001.

Paul SolerUniversity of Glasgow and

Rutherford Appleton Laboratory

(on behalf of LHCb RICH group)

III LHC Symposium, Chia, Sardinia, 29 October 2001

2

Participating InstitutesParticipating Institutes

Imperial College

University of Bristol

Rutherford Appleton Laboratory

University of Oxford

University of Edinburgh University of Glasgow

CERNSezione di Genova

Sezione di Milano


3

LHCb ExperimentLHCb Experiment LHCb Detector: forward single arm spectrometer

Acceptance:10-300 mrad bending

10-250 mrad non-bending

RICH1

RICH2


4

Particle IdentificationParticle Identification

Excellent Particle Identification (-K separation) required from 1 - 150 GeV/c

RICH system divided into 2 detectors and 3 radiators: aerogel, C4F10, CF4

Momentum vs polar angle

Momentum


5

RICH1 RICH2

RICH System OverviewRICH System Overview

Acceptance– 300 mrad RICH 1

– 120 mrad RICH 2

Radiators: thickness L, refractive index n, angle c, /K threshold

Aerogel C4F10 CF4

L 5 85 167 cm

n 1.03 1.0014 1.0005

c 242 53 32 mrad

0.6 2.6 4.4 GeV

K 2.0 9.3 15.6 GeV

Photo detectors


6

Photo DetectorsPhoto Detectors Photo detector area: 2.6 m2

Single photon sensitivity: 200 - 600 nm, quantum efficiency > 20%

Good granularity: ~ 2.5 x 2.5 mm2

Large active area fraction: 73% LHC speed read-out electronics:

40 MHz

LHCb environment: magnetic fields,

charged particles

Hybrid Photodiodes (HPD) baselineHybrid Photodiodes (HPD) baseline

CF4

Aerogellarge rings

C4F10

small rings

Multi-Anode PMT (backup)Multi-Anode PMT (backup)


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Quartz window, thin S20 photo cathode QE dE = 0.77 eV

32 x 32 Si pixel array: 500 m

(Canberra) ~450 tubes for RICH system Cross-focusing optics

– demagnification ~ 5

– 50 m point-spread function

– 20 kV operating voltage Encapsulated binary electronics Tube, encapsulation: industry (DEP)

Hybrid Photo Diodes (HPD) Hybrid Photo Diodes (HPD)

Pixel HPD (baseline)Pixel HPD (baseline)

-20 kV

61 pixel HPD61 pixel HPD Existing prototype

external read-out = 80 mm


8

HPD R&D ResultsHPD R&D Results

TestbeamTestbeam

CherenkovPhotons

CherenkovPhotons

Testbeam Setup– RICH 1 prototype– 3 HPDs

Figure of merit– N0 202 cm-1 (~35 PE/ring)

Single photoelectronspectra visible


9

HPD ElectronicsHPD Electronics

ALICE / LHCb development

(0.25 m CMOS) ALICE pixel size 50 m x 425 m LHCb pixel size 62.5 m x 500 m

8 pixels = 1 LHCb super-pixel

500 m x 500 m 40 MHz read-out clock Bump bonding: chip-sensor

Pixel chipPixel chip

50 m

OccupancyMax Mean

RICH 1 8.2% 1.2%RICH 2 2.6% 0.4%


10

Pixel HPD Chip StatusPixel HPD Chip Status Chips received: only operate up to 10 MHz (ALICE requirements) Bump-bonding sensor-pixel chip: VTT Finland, good quality Lab tests within LHCb requirements:

– Threshold scans: ~700 e- (<2000 e-)

– Noise: ~90 e- (<250 e-)

– Signal: ~5000 e-

Wire bonding to ceramic carrier: Edgetek (Paris), good quality LHCb chip redesign to achieve 40 MHz: submission IBM November

– All current and voltage DACs redesigned and correctly layed-out

– Improved uniformity of pulser

– Clock skew being improved HPD Pixel chip resubmission after October: review 31 October, 2001

HPD pixel chip assemblywith ceramic carrier


11

Magnetic Field TestsMagnetic Field Tests Prototype with a phosphor screen anode

read out by a CCD (resolution ~150 m) for magnetic field tests.

Distortions tolerable up to 10 Gauss Flipping of B field shows no change in

position residuals (within resolution).

Axial field Transverse field


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MAPMT (backup)MAPMT (backup)

8x8 dynode chains, pixel 2x2 mm2 (effective size with lenses 3.2x3.2 mm2)

Gain: 3.105 at 800 V UV glass window, bialkali photo cathode:

QE = 22% at = 380 nm Test beam data: 6.51 0.34 p.e. Expect from simulation: 6.21 p.e.

Multianode Photo Multiplier TubeMultianode Photo Multiplier Tube

MAPMT active area fraction: 38% (includes pixel gap)

Increase with quartz lens with one flat and one curved surface to 85%


13

RICH1 EngineeringRICH1 Engineering

Kapton beam-pipe seal

Mirrors

Photo detectors

14% X0

Beam-pipe


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AerogelAerogel

# photoelectrons vs. thickness

5cm

transmission vs. dose

LHCb 1 year

104 Gy

Hydroscopic Aerogel provides the best quality– clarity: 0.0045 m4/cm-1

– refractive index: 1.034– radiation hard– Thickness: present choice 5 cm


15

Baseline: glass mirrors with 3-leg spider

(carbon fiber with screw adjusters)

Minimize dead material within acceptance

Alternatives:

glass 6mm : ~ 4.5% X0 , 1.5% l

berillium 5mm : ~ 2% X0 , 1% l

composite : ~ 1% X0 , 0.5% I

spiderprototype

spiderprototype

adjusteradjuster very good

repeatability &

stabilitybeam pipebeam pipe

330 mrad acceptance

one quadrant ofspherical mirrors

beam pipebeam pipe

RICH1 MirrorsRICH1 Mirrors


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entry windowlow mass

beam pipe envelopesupported by windows

spherical mirrorson supporting planes

exit windowlow mass

photodetectorswith individual magnetic shields

magnetic shield box& backward lid (4 tons)

to shield against magnetic stray fieldof ~150 Gauss

frame

planemirrors

12.4% X0


17


increasingdeflection

– Natural frequencies

Fundamental frequency ~6Hz

Negligible movement

Finite Element Analysis:– Deflections under load

(mag. shield 2x11000kg, tracker unit 200kg)

max. deflections <5mm achievable


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RICH2 Gas EnclosureRICH2 Gas Enclosure

window400Pa

Photodetector window

1500x750x5 mm (two plates) Optical transmission:

>90% above 200 nm

External Transmission

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

150 160 170 180 190 200 210 220 230

Wavelength (nm)

Transmission(%/5mm)

RAL requirements

Actual measurements

Gas enclosure windows sealed at beam pipe and frame 1mm fibre skins + 48mm PMI foam core: ~30mm at 400Pa Stress on beam pipe sheet: @ 400Pa: ~1 ton

Tube

Flange


19

RICH ElectronicsRICH Electronics Pixel chip

– encapsulated, binary, 40 MHz, 32:1 MUX

Level 0 – on detector– Gbit optical links– clocks, triggers - TTC

Level 1– in counting room– buffers data L1 latency,

transports to DAQ– zero suppression– TTC, DCS interface


20

Electronics Test BenchElectronics Test Bench

Light box

X-yL1

PC

JTAGcontroller

PCI-FLIC

S-link

S-linkOL

HPD assembly

L0

HV

HV control

X-y controller

dTAPdTAP

dTAP

dTAP

TTCrxfpPINT

TTCrx

L0:photo detector test bench

L1:stand alone or VME crate

DAQ PC:DAQ & control

Stand alone system for demonstration and test bench use Nearly final setup (no TTCrx, ECS, DCS) available 01/2002


21

Photodetector Test FacilitiesPhotodetector Test Facilities ~500 HPD or ~4000 MaPMT to be tested for:

– functionality within specifications

– individual characteristics

– working parameters full automation needed

selection of detectors according to test results

– position in detectors wrt. occupancy to be operational in mid 2002 in the case of HPD’s:

– use the electronics test-bench system

– estimated time for all measurements & scans

for one tube: 24hrs

(including handling and resting in the dark) 2 test facilities needed for 1 1/2 years

(Edinburgh & Glasgow)

MaPMT test setupMaPMT test setup

xy-tablexy-table

ODEODE

MaPMTMaPMT


22

RICH Gas and MonitoringRICH Gas and Monitoring

RICH-2

Ultrasound

Fabry-Perot additionalmonitor systems

by LHC Gas group control & monitor p & T

Ultrasound gas monitor:– Measure variation of

sound speed

v = (RT/M)1/2

monitor gas composition Fabry-Perot monitor:

– Measure fringes (depend on distance d, , and n)

monitor dispersion n()


23

RICH AlignmentRICH Alignment Misalignment mirrors: fit photons from data to

= A cos(sin( In RICH2 (two mirrors): can only perform

relative alignment Minimise for two mirror tilts Photons from ambiguous mirror

combinations (20%) degrade performance Seed alignment <1 mrad for no degradation

1 mrad misalignment


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RICH PerformanceRICH Performance Simulation

– based on measured test beam HPD data

– global pattern recognition – background photons

included

# of detected photons– 7 Aerogel 33

C4F10 18CF4

Angular resolution [mrad]

– 2.00 Aerogel 1.45C4F10 0.58CF4

3 -K separation3-80 GeV/c

(21-150 GeV/c


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BBdd -> -> ++

sensitive to CKM angle ~ 20 - 50 in 1 year

– depends on |P/T| and strong phase

Backgrounds also have

Tree T Penguin P


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BBss -> D -> DssKK

Rate asymmetries measure angle

Expect 2400 events in 1 year of data taking


27

ConclusionsConclusions Physics performance studies show that the RICH is

essential for the LHCb physics programme. The RICH design of LHCb with two detectors and

three radiators provides 3 -K separation from 3-80 GeV/c

LHCb RICH is progressing since TDR– Pixel HPD chip has incurred a delay but is not in

critical path (project under review).– Design for subsystems are detailed and advanced– Transition from R&D to construction

In time to take data when LHC becomes

operational in 2006

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